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LOWER GI PATHOLOGY - Coggle Diagram

- - - - active chronic inflammation - acute + evidence of chronicity
        
        crypt abscesses (neutrophil infiltration into lumen of crypts)
  - - - pseudomembranous colitis
        
        due to C. difficile infection following broad spectrum antibiotics
        
        neutrophils form 'membrane' on top of mucosa
      - acute inflammation, neutrophils, mild crypt loss
      - watery diarrhoea, colicky abdominal pain, fever
  - - - usually superficial
        
        if penetrates through the colon wall, causes infarction
      - mixed acute and chronic inflammation, crypt loss
    - - causes: arterial/venous occlusion, vasculitis, intestinal obstruction
      - most commonly occurs in the watershed area around splenic flexure/descending colon
        
        between supply of middle and left colic arteries
  - - - outpouching of mucosal wall (where muscle is weakest)
        
        bacteria can overgrow here
        
        if obstructed, they perforate or form diverticular abscess
        
        bleeding, perforation, abscess, fistula (if adherent to other structures), stricture
  - - - Ulcerative colitis
        
        acute
        
        marked hyperaemia and irregular ulceration
        
        diffuse active inflammation confined to mucosa
        
        basal plasmacytosis, crypt distortion
        
        chronic
        
        diffuse ulceration with focal residual mucosa
        
        pseudopolyps (formed by regenerating mucosa)
        
        total mucosal atrophy and crypt flattening (late)
        
        complications
        
        toxic megacolon (perforation)
        
        dysplasia and carcinoma (>20 years)
      - Crohn's disease
        
        involves any site in GIT (most commonly terminal ileum)
        
        patchy (skip lesions)
        
        affects full thickness of bowel wall
        
        deep fissures
        
        muscle and neural hypertrophy
        
        granulomas in 50%
        
        collection of epithelioid histiocytes (macrophages)
        
        longitudinal ulceration with sharp demarcation
        
        cobblestone appearance (due to regenerating mucosa between ulcerations)
        
        fat wrapping
        
        thick rigid wall
        
        complications
        
        adhesions, perforations, abscess, fistula, stricture, dysplasia/carcinoma
- - - - glandular epithelium
        
        adenoma (polyp)
        
        carcinoma
        
        abnormal glandular tissue
        
        sessile (flat on surface)
        
        pedunculated (long stalk of mucosa)
        
        neoplastic
        
        adenomatous polyp
        
        tubular adenoma
        
        typically pedunculated
        
        villous adenoma
        
        typically sessile
        
        tubulovillous adenoma
        
        chromosome instability pathway
        
        oncogenes (e.g. ß-catenin) and tumour suppressor genes (e.g. APC, e-cadherin)
        
        1 more item...
        
        serrated polyp
        
        traditional serrated
        
        sessile serrated
        
        microsatellite instability pathway
        
        1 more item...
        
        non-neoplastic
        
        reactive (inflammatory or traumatic)
        
        hyperplastic
        
        hamartomatous (developmental)
        
        Peutz-Jegher's polyp
        
        juvenile polyp
        
        most polyps are sporadic not genetic
        
        familial polyposis syndromes
        
        familial adenomatous polyposis (FAP)
        
        100+ polyps
        
        1 more item...
        
        total colectomy
        
        autosomal dominant mutation of APC gene (Ch5)
        
        attenuated FAP
        
        MYH or APC gene (other loci)
        
        less than 100 polyps
        
        1 more item...
        
        lynch (HNPCC)
        
        less than 100 polyps
        
        1 more item...
        
        DNA mismatch repair genes MSH2/MLH1/MSH6/PMS2
      - neuroendocrine cells
        
        neuroendocrine tumour